Resumo

ZANATTA, Tiago; REIS, Erlei Melo  e  ZANATTA, Mateus. Adjuvant concentrations and uredospore densities on Phakopsora pachyrhizi infection efficiency in soybean. Summa phytopathol. [online]. 2012, vol.38, n.2, pp. 148-151. ISSN 0100-5405.  http://dx.doi.org/10.1590/S0100-54052012000200007.

Experiments were carried out in a growth chamber to evaluate the effect of spreader and uredospore concentrations on the efficiency of infection by Phakopsora pachyrhizi, the causal agent of Asian soybean rust. CD 214 RR soybean cultivar was inoculated with the following polyoxyethylene sorbitane monolaurate concentrations: 0, 30, 60, 120, 240, 480 and 960 µL.L^-1 water, as well as a fixed uredospore concentration of 2 x 10⁴ spores.mL^-1. In a second phase, the inoculum concentrations of 0, 5 x 10³, 1 x 10⁴, 2 x 10⁴, 4 x 10⁴, 8 x 10⁴ and 16 x 10⁴ uredospores.mL^-1 were evaluated, and the spreader concentration of 240 µL.L^-1, selected in the previous experiment, was fixed. The spreader concentration of 240 µL.L^-1 can be used in artificial inoculation studies, as well as up to 4 x 10⁴ uredospores.mL^-1. In this work, there was a correlation between uredia and lesion density. Thus, the use of lesion density is recommended to assess disease intensity for its accuracy and less time consuming. There was also a positive correlation between uredia and lesion density.

Palavras-chave : Leaflet incidence; lesion density; Asian soybean rust; Glycine max.